Conventionally, rollers covered by resin tubes or fiber-like substances have been used as rollers in conveyors and other such conveyor apparatuses and as rollers in conveyor units in printing apparatuses. Furthermore, among the rollers which are employed for feed, movement, or conveyance of sheet-like objects through utilization of friction, solid rubber rollers which have high coefficient of friction are usually employed. Where such a roller conveys as conveyed object in the form of sheet-like paper, film, fabric, or the like, paper dust, dust, fibrous waste, and the like will adhere to the surface of the roller, causing degradation of conveyance characteristics. To address this, rollers in which recesses and projections are provided at the surface of the roller and the like have been proposed, these being employed in a variety of apparatuses. Furthermore, to prevent paper dust, dust, fibrous waste, and the like from adhering to the roller surface, rollers covered with tubes comprising fluorocarbon resin having low coefficient of friction, and apparatuses that clean roller surfaces on which paper dust, dust, fibrous waste, or the like has adhered, have been developed.
Moreover, as suction rollers having air permeability for cooling or suction, rollers having a multiplicity of suction holes formed at the surface thereof and rollers which are cylindrical bodies having a multiplicity of slits formed therein and which are formed such that fibril-like material is wound thereabout have been developed, these being used as rollers in apparatuses for manufacture of resin film and/or sheet. It so happens that in connection with rotary presses which are printing apparatuses, from the standpoints of improvement of quality and improvement of productivity, and from the standpoint of maintaining a clean environment as well, apparatuses and rollers capable of conveying printed matter without coining in contact with the surfaces of the printed matter that are coated by ink are desirable.
On the other hand, as a paper feed apparatus for a printer, an apparatus comprising a cover member made of woven cloth has been proposed in which an outer surface of a shell is coated with a low-friction material, this is further covered with a cover member made of woven cloth, this cover member made of woven cloth is impregnated with an ink-adhesion-preventing agent and is moreover formed into the shape of a cylindrical seamless sleeve having open ends (see, for example, Patent Reference No. 1).
Moreover, as a roller for conveying that can be easily covered by anyone and that is capable of being manufactured at low cost, a cover has been proposed in which yarn comprising heat-shrinkable fiber that has been coated by silicone resin having plentiful lubricity, mold-releasability, and wear resistance is employed to manufacture a seamless tube comprising knit fabric, braided fabric, or woven fabric, this seamless rube being used to cover the outside circumference of a roller core (see, for example, Patent Reference No. 2).
Moreover, there has been a proposal in which water-soluble polyvinyl alcohol fibers are stranded together in a reversible pattern to form a cylindrical knit fabric, this cylindrical kin fabric being used as cover material to cover a roller for conveying magnetic tape (see, for example, Patent Reference No. 3).
Furthermore, in the context of a roller for conveying plate glass which has been softened by heating, to achieve increase in the life of a sleeve comprising fiber knit fabric which covers a roller core member and reduction in plate glass manufacturing and processing cost, a glass conveying roller has been proposed which is a roller for conveying plate glass which has been softened by heating and in which a sleeve comprising knit fabric made of heat-resistant inorganic fiber is used to cover the outside circumference of a roller core member, a protective covering moreover being arranged at the surface of said sleeve (see, for example, Patent Reference No. 4).
Moreover, a conveying roller ensuring interfacial peel strength has been proposed which is a conveying roller that, even without use of adhesive, has adequate required metal core/fluorocarbon resin tube interfacial peel strength, and in which, in causing the outside circumferential surface of the metal core to be covered by a heat-shrinkable tube made of fluorocarbon resin, at the outside circumferential surface of this metal core, taking the outer contour in the circumferential direction of the metal rod stock constituting the metal core starting material as an imaginary line, groups of peak-like ridges that protrude beyond this imaginary line are formed in regular fashion in a parallel state on the outside circumferential surface of the metal core, at which time the depth of the valleys between mutually adjacent groups of peak-like ridges is made to be at least 0.05 mm, as a result of which the conveying roller is such that interfacial peel strength is ensured even when adhesive is not used in combination therewith, permitting achievement of prevention of dislocation and improvement in productivity (see, for example, Patent Reference No. 5).
Moreover, a suction roller has been proposed which is a cylindrical body having a multiplicity of slits formed with fibril-like material wound thereabout, and formed such that engaged with this cylindrical body is a tubular object comprising wire mesh, screen, nonwoven fabric, woven fabric, or paper comprising synthetic fibers or natural fibers, or plastic or metal which is porous (see, for example, Patent Reference No. 6).
Furthermore, a sheet conveyor apparatus has been proposed for increasing intimacy of contact between a suction roller and a sheet traveling along the outside circumferential surface thereof, for permitting definitive correction of positional dislocation due to travel, and for causing offset defects not to be produced, which is a sheet conveyor apparatus equipped with a suction roller that supports a moving and traveling sheet at the outside circumferential surface thereof, this suction roller being such that formed at the outermost peripheral surface region of a cylindrical roller made of metal there is a mesh cylinder in which a multiplicity of suction holes of diameter not greater than 1 mm are formed through creation of openings by means of etching (see, for example, Patent Reference No. 7).
Moreover, a roller has been proposed which comprises a rubber elastic body in which a multiplicity of grooves for attenuation of wear are formed at the outside circumferential surface of a roll that comes in contact with a sheet-shaped article (see, for example, Patent Reference No. 8).
As indicated at the foregoing Patent References, cover materials for rollers include woven fabric, paper, nonwoven fabric, wire mesh, and knit fabric, as well as rubber tubing, shrink tubing, and so forth. Furthermore, cover materials on which coating or other such treatment has been carried out, coverings comprising heat-resistant materials, knit fabrics in which elastomers have been embedded, and the like have been developed. However, with conventional coverings, where the covering is constituted from a fibrous or filamentous substance, rubbing contact with the conveyed object and compression under load has caused occurrence of fraying due to breakage of filaments, and as this fraying has progressed it has caused occurrence of problems affecting conveyance characteristics and other such functions. Furthermore, with such rollers, for maintenance of gripping characteristics or surface protection, coating treatment is carried out in which a coating agent is used to impart the surface of the roller with a coating layer, so as to improve the coefficient of friction or protect the underlying fabric. However, where coatings are employed, sliding contact causes the coating layer to wear, as a result of which there is the problem that life is shortened. To increase life, it therefore becomes necessary to increase the thickness of the coating layer, as a result of which there is the problem that manufacturing cost is increased.
With rollers covered with the foregoing rubber tubing, shrink tubing, and other such covering materials, tubing materials include fluorinated-type, polyolefin-type, and silicone-type, as well as PET, PVC, rubber-type (EP rubber), and so forth, and there is also woven fabric, knit fabric, and so forth. Where tubing comprising such materials is employed there will be the problem of achieving adhesion to the core. For adhesion to the core, heat-shrinkable tubing which is made to contract through use of heat is therefore typically used. In addition, where lubricity or the like are required at the surface, resin-type heat-shrink tubing is employed; and in particular where low coefficient of friction is required, fluoro-type heat-shrinkable tubing is employed. Furthermore, where gripping characteristics are required at the surface, rubber-type tubing is employed.
Where such resin-type heat-shrink tubing is employed, it is ordinarily the case that circumstances related to tubing manufacturing method cause the surface to be slippery and to have poor gripping characteristics. They are therefore not suited for applications where conveyed objects are conveyed under low load. But in apparatuses where rollers act together to form a nip at high load to allow gripping force to be obtained, resin-type heat-shrink tubing is often used. Moreover, because fluoro-type and silicone-type resin tubings are heat-resistant, these are employed in rollers that undergo heating. However, with rollers employing such resin tubing, because circumstances related to manufacture of the tubing cause the inner and outer surfaces to be slippery, while they are appropriate as rollers where smooth surfaces are required, occurrence of slipping and the like can result in feed nonuniformities in applications where conveying occurs with nips at low loads. Moreover, where scratches or the like appear on the tubing, contaminant adheres to such scratches, as a result of which defects are produced on the conveyed object. With tubing comprising knit fabric, heat-shrink fiber is employed at the yarn and heat-shrinking is carried out to achieve intimate contact with the core, but there is the problem that there is fraying of yarn at the end faces of the tubing. Processing at the end faces is therefore required.
Next, with rollers used for ventilation, for cooling, or for suction, because holes are ordinarily formed on the surface of the roller, there is the problem that processing costs for carrying this out are high. To address this, Patent Reference No. 6 discloses a suction roller in which there is a roller produced by winding a fibril-like material about the surface of a cylindrical body on which a multiplicity of slits have been formed, and screen, nonwoven fabric, woven fabric, or paper comprising synthetic fiber or natural fiber, or a porous substance comprising plastic and/or metal which covers and engages with the outside surface of the cylindrical body. However, where a covering comprising ordinary woven fabric covers and engages with a cylindrical body, with conventional mesh-like woven fabric having air permeability, being nothing more than the intersections of warp yarn and weft yarn, there is a tendency for occurrence of fraying due to breakage of yarn and of runs in the material as a result thereof, and there is moreover a need to carry out prevention of fraying at the open ends of the cylindrical covering. In addition, with a roller covered with ordinary knit fabric or woven fabric, because no antislip function is carried out to prevent sliding relative to an object when the roller is rotating, it is necessary to secure this with adhesive or the like at location(s) where it contacts the core. Furthermore, in the context of a suction roller for carrying out suction, to carry out conveyance without damaging the surface of a sheet, suction holes are provided at the surface of the suction roller by means of the method in which holes are formed at the surface by etching and the fraying prevention method described above (see, for example, Patent Reference No. 7). Thus, with suction rollers, i.e., rollers which utilize suction, problems include damage to the surface of the sheet, positional dislocation during travel due to conveyance, offset defects, and the like, as a result of which fabrication of micropores, damage to the roller surface, burrs, and so forth are problems. These have therefore also been a factor in increasing cost as attempts have been made to improve the foregoing.
Moreover, with conventional ordinary rubber rollers which are rollers such as may be employed for conveyance or feeding of paper and the like, rubber rollers made up of rubber layer(s) at the surface thereof have such problems as the fact that gripping characteristics with respect to paper deteriorate due to contamination at the surface as a result of paper dust or the like and wear of the surface, and the fact that there will be misfeeds and so forth in accompaniment to this deterioration in gripping characteristics. This being the case, in order to deal with this, a construction has been adopted in which recesses and projections are provided at the surface of the rubber roller, and/or improvements have been made to the rubber material. Moreover, because the rubber roller surface is solid, there has been the problem that it has been impossible to avoid contamination due to accumulation of dust at the rubber surface, some apparatuses even being provided with a member which carries out cleaning of the roller surface. Conventional rollers thus include a wide variety of rollers, and roller mechanisms compatible with applications are known. In addition, various apparatuses for which conservation of resources, conservation of energy, recycling, and low cost are desired, as well as rollers and roller mechanisms for use with such apparatuses, have become necessary in recent years.